higher octane will increase engine heat which is undesirable but will not give greater performance unless the engine is designed for it. My guess is if you went to a lower octane you would not notice a differenced. When the HT motor was designed leaded gas was still used at something like 78 octane. Thats not to say if your riding around on a 30(F) degree day it would make a difference.

Higher octane fuel doesn't run hotter or produce more power, it does have more resistance to the condition called detonation. This is the result of compression induced firing rather than spark induced firing. Running higher octane fuel, than required, won't effect anything other than your wallet.

Higher octane fuel doesn't run hotter or produce more power, it does have more resistance to the condition called detonation. This is the result of compression induced firing rather than spark induced firing. Running higher octane fuel, than required, won't effect anything other than your wallet.

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I couldn't agreemore with this statement.
Unless you have a very high compression racing motor, running high octane fuel in a h.t. motor is just throwing your money out the exhaust pipe.
these motors were designed to run on "regular" gas (92 octane or so)

I agree, considering their history, these generic chinese 2 strokes will run fine on poor quality fuel and high octane is just throwing money out the window. Buttttttt, I hear that premium fuel (at least here in the USA, and not in Hajuuland) is likely NOT to contain any ethanol. This is better for storage, as the gasahol (10% blend) that is sold as gasoline can suffer from "phase separation" when stored under certain conditions. This causes driveability issues and possible engine seizure with a 2 stroke. Just ask any outboard tech and he'll tell you all about it.

Where I live, the regular unleaded pumps will indicate that the fuel will contain "up to" 10% ethanol. Some will even tell you outright that the fuel is 10% ethanol. The premium pumps have no such label. Even then, I am not 100% sure. You hear a lot of static on the intarwebs.

....never had an issue in my two strokes running regular or my 460 on premium.

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Oooooh - just caught the "460" reference. Those little engines can scream!
Currently, I am working on a minimoto (cagliari or "cag") engine on a BMP friction drive kit. I bought the kit a few weeks back (scratch n' dent special) but haven't had the time to prep an engine or bicycle. Just ordered the engine, now I need to figure out an exhaust and a gas tank setup. The little cag motors are not nearly as good as the GP460's but they aren't too shabby. I hear that the cags need premium fuel too, especially when running a "rockit" key to advance ignition timing.

Fuel grade (octane requirement) is a function of compression ratio. If the manufacture recommends a fuel with a octane rating of 87, nothing will be gained running higher octane fuel. The "logic" that if it cost more, it must be better, doesn't always work. In any event, during the break in period, the engine will have lower compression.

another point to consider, premium fuel will have less if any ethanol like someone else stated, which dries out gaskets and seals in the carburetor. We like to run premium fuel in any small engine we repair at work. (I am a small engine mechanic by trade) The EPA is even trying to make it so all gasoline sold is 15% ethanol content, but the small engine manufactures are all trying to fight that as small engines will not run right on 15% ethanol blend and the ribber diaphragms used in the carbs for fuel pumps will not hold up to it along with other issues.

When I get my 80cc 2 stroke kit, I am going to deck the head to raise compression to better match premium fuel. It will give me more bang for the buck, for little cost.